Method for the production of viscose solutions



Patented July 4, 1950 v' I un; so.

Industria-l .ilyayonsCbx-poratinn, `.Glevelan d,`. Ohio, wcomorationzoflllware is commonly.. steepedlrin an aqueou caustic;- sod'a, 10

solution.. ofj.' 18`-.-19.'%.L concentrati'om av controlled-.3 temperatures` for abouti. ones hours'. alkali; cellulose .tlius'zformed.` iss-.pressedito removerexcess@ aqueous. caustic solutiom Aitor.y shredding@ the pressed alkali" cellulose into .cr1unbs,=.the material@ 15- aged under;. controllectl. condition l andalsubsen quently converted?! into.. cellulose;` xanthatei. by;v treatment in. aLcIosed.. cliamber'L vsfitli carbon-fz.A sulle'. '11o producetliesfinalt viscose@:spil'iningay aret dissolvedl. in, aqueous-caustic; sodas solutions. The normakcausticity..offl-viscosersolutionssmproe" duced;A isgbetvveene 5 `.%1 .and.`..8l%`} .by-L Weigltxt,A

. the xanthation methodtemployew'mostgene eralIy; a batchbflallali cellulose#crumbsshavingf: 25

is'rjso termedf because@ nowaqueouse solutionse are;l 30.`

introdce'd` eitherzbefre, duing'frorattermantha-` tion', thus. maintaining.gthe;,clillmscomp'aratively:` dry; In thiszmetliocb..carbon..disulliiea.issintrmA duced'intoth'e chargedrotatingliurnanther after thel rotationcontiuedtfmaeperiod; ofgfrom': 35;.

dropped "and"rakedfoutofthe churn into adis, 40

soltingj vessel." Thereaten.. au. fresh. charge. of(Y alkali cellulose crumb's is,introdii'ced...into'.i the# churn.l and the processi repeated? lin.. an identical;- manner'from Abatich to biatch'.

Another 'methodlwhicl liassbeenproposed'in; 45

crumbs; aqueoussolutions-areiintrorlucedinto'the.: 50.

churn: In Wet churn?? 'xantli'atngv methods`,..asgl prop osed heretofore, a'. batch ofl'l alkali l cellulose crumbs, Having.; abouti tHe; same.. physical.. andl chemical` characteristics-msi the .ecrlumbszemploye d.

in the dry-churn?! methodsis'a'chamedsintorar56 determinedi-quantity.ofwater is introduced intoffthechurnandtthe. mass agitated to form.- aI slurry? of the..xanthated.. crumbs.- After thel slurry-has-t been. discharged.n into a xanthate. dissolver;. af. smaller'quantityofy aqueous caustic sodaX solution, containing.v alLof. the. causticrequired.` fonthef: dise solving.. step,. is'tintroducedff intoh the-churn1n Ins thismethod the.. caustic solution must necessarily: hav-cfa causticityA notless-.andpreierablyygreaten' than .fthat of the .alkali cellulose Jcrumbs, .that tis;-A about l5.%,. anniy preferably greater;.i..ef-, 181%2?. Thereafter, such1caustic'wash solution: is agitatedi Within. the churn, dischargedtand combined-with@ the previouslydischarged slurry tov form a viscose:L spinnngsolution4 yotuesireot composition..v 'Il'ieree-` after, another batch of alkali cellulose is charged, into. the -churn While .the churn..isstil1.Wetewith the, final caustic.. Wash .4 solution. of theX previous?- batch.

Ashas been `previously indicated, tlfiemethod's-f` heretofore proposed have avoided.. employing.. ai'. nal caustic churnV Wash. solution having; as causticity less.. than that.. of the; alkali f cellulose:r crumbs. This.` is dueI toa belieflthatla'nm dr'ained,`.. carryi-over, caustic. Wash solution-1. re maihing. in.. a.. churn. .might leachvout/fthe; causticffrom.. the succeeding. batches.,of.' alkalicellulose and'thus impair.. the. reactivity., of. I such f. batches with .carbonbisul'dec Thusinworder top roducef; viscose of normaljcaustie composition,..i.2 e'., 5%.1: tok 8%', under such ,churn-wash..limitationsfitvisl essential itliatV the volume. of vvthe.nalfwasli..solua tion" of.. each .batclLbe much. smaller. than' tlie; volume of" the. preceding. slurry solutionf... Underr these conditions .it has beenffoundthatlth'e secondi.. and' succeeding Xanthatebatches :ofi a.. serieseofrl batches produce viscoses. which' containeXcess,

amounts of unxanthated.. fibers and.; have.. poom lterablity properties.

It is believedjfthat the. chief sourceof ',tliediY-l cultes'.I arising` out otfth'e use .oiflvvetf xanthating.; churn's. as' heretofore proposed.i`s..the. continualfi` presence; in. the churns, of 'undsctargedviscoseelikematerial or viscose.- containing. particles. and;` residues which" are' carri'ed.' overv from.. batch.. totv batch.. BSI.. viscoseflikef. materials andi viscose.- con-taining materials is .meant partial-lyrwholly. dissolved .cellulose Vxarithatesthat .ares not lin l the: same `plzrysical.statevas the .-nal:avisoosetspinningv. solution knit-1y are; nevertheless'g.. quite:v similar chemically. These materials..- appear-.z as fluide..

I claim:

1. In the process of forming a viscose solution in which process a quantity of alkali cellulose having an alkalinity of the order of about NaOI-I by weight is introduced into a churn and treated with carbon disulde to form sodium cellulose xanthate and in which an aqueous caustic soda solution is thereafter admixed with said formed cellulose xanthate and the mixture discharged into a dissolving vessel to form a viscose solution the steps comprising; scavenging said discharged churn at least once with an aqueous caustic soda solution having an alkalinity less than that of said alkali cellulose; discharging said scavenging solution from said churn; combining in a dissolving vessel substantially all of said discharged scavenging solution with said previously discharged mixture to form a Viscose solution having an alkalinity between about 5% and 8% NaOH by weight; thereafter introducing another quantity of alkali cellulose into said churn While said churn is still wet with scavenging solution; and repeating the cycle.

2. In the process of forming a viscose solution in which process a quantity of alkali cellulose having an alkalinity of the order of about 15% NaOH by weight is introduced into a churn and treated with carbon disulfide to form sodium cellulose xanthate and in which an aqueous caustic soda solution is thereafter admixed with said formed cellulose xanthate and the mixture discharged into a dissolving vessel to form a viscose solution the steps comprising; scavenging said discharged churn at least once with an aqueous caustic soda solution having an alkalinity less than that of the viscose ultimately produced; discharging said scavenging solution from said churn; combining in a dissolving vessel substantially all of said discharged scavenging solution with said previously discharged mixture to form a viscose solution having an alkalinity between about 5% and 8% NaOH by Weight; thereafter introducing another quantity of alkali cellulose into said churn while said churn is still wet with scavenging solution; and repeating the cycle.

3. In the process of forming a viscose solution in which process a quantity of alkali cellulose having an alkalinity of the order of about 15% NaOI-I by weight is introduced into a churn and treated with carbon disulde to form sodium cellulose xanthate and in which an aqueous caustic soda solution is thereafter admixed with said formed cellulose xanthate and the mixture discharged into a dissolving vessel to form a Viscose solution the steps comprising; scavenging said discharged churn at least once with an aqueous caustic soda solution, both said previously admixed aqueous caustic solution and said scavenging solution having alkalinities less than that of the viscose ultimately produced; discharging said scavenging solution from said churn; combining in a dissolving vessel substantially all of said discharged scavenging solution with said previously discharged mixture to form a viscose solution having an alkalinity between about 5% and 8% NaOH by weight; thereafter introducing another quantity of alkali cellulose into said churn while said churn is still wet with said scavenging solution; and repeating the cycle.

4. In the process of forming a viscose solution in which process a quantity of alkali cellulose having an alkalinity of the order of about 15% NaOH by Weight is introduced into a churn and treated with carbon disulfide to form sodium cellulose xanthate and in which an aqueous caustic soda solution is thereafter admixed with said formed cellulose xanthate and the mixture discharged into a dissolving vessel to form a viscose solution the steps comprising; scavenging said discharged churn a plurality of times with aque ous caustic soda solutions having alkalinities less than that of said alkali cellulose; discharging said scavenging solutions from said churn; combining in a dissolving vessel substantially all of said discharged scavenging solutions With said previously discharged mixture to form a viscose solution having an alkalinity between about 5% and 8% NaOH by weight; thereafter introducing another quantity of alkali cellulose into said churn while said churn is still wet with scavenging solution; and repeating the cycle.

5. A process according to claim 1 in which Wan ter is introduced into the discharged churn as a scavenging solution.

6. In the process of forming a viscose solution in which process a quantity of alkali cellulose having an alkalinity of the order of about 15% NaOI-I by weight is introduced into a churn and treated with carbon disulfide to form sodium cellulose xanthate and in which an aqueous caustic soda solution is thereafter admixed with said formed cellulose xanthate and the mixture discharged into a dissolving vessel to form a viscose solution the steps comprising; scavenging said discharged churn a plurality of times with an aqueous caustic soda solution and agitating said scavenging solutions in said churn; both said previously admixed aqueous caustic solution and said plurality of scavenging solutions having alkalinities less than that of the viscose solution ultimately produced; discharging said scavenging solutions from said churn; combining in a dissolving vessel substantially all of said discharged scavenging solutions with said previously discharged mixture to form a viscose solution having an alkalinity between about 5% and 8% NaOH by weight; thereafter introducing another quantity of alkali cellulose into said churn while said churn is still Wet with scavenging solution; and repeating the cycle.

EMIL KLINE.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,807,370 Bernard May 26, 1931 2,338,196 Nash l Jan. 4, 1944 FOREIGN PATENTS Number Country Date 456,841 Great Britain Nov. 16, 1936 OTHER REFERENCES Vollrath Rayon Textile Monthly, page 49, July 1936` 

1. IN THE PROCESS OF FORMING A VISCOSE SOLUTION IN WHICH PROCESS A QUANTITY OF ALKALI CELLULOSE HAVING AN ALKALINITY OF THE ORDER OF ABOUT 15% NAOH BY WEIGHT IS INTRODUCED INTO A CHURN AND TREATED WITH CARBON DISULFIDE TO FORM SODIUM CELLULOSE XANTHATE AND IN WHICH AN AQUEOUS CAUSTIC SODA SOLUTION IS THEREAFTER ADMIXED WITH SAID FORMED CELLULOSE XANTHATE AND THE MIXTURE DISCHARGED INTO A DISSOLVING VESSEL TO FORM A FISCOSE SOLUTION THE STEPS COMPRISING; SCAVENGING SAID DISCHARGED CHURN AT LEAST ONCE WITH AN AQUEOUS CAUSTIC SODA SOLUTION HAVING AN ALKALINITY LESS THAN THAT OF SAID ALKALI CELLULOSE; DISCHARGING SAID SCAVENGING SOLUTION FROM SAID CHURN; COMBINING IN A DISSOLVING VESSEL SUBSTANTIALLY ALL OF SAID DISCHARGED SCAVENGING SOLUTION WITH AID PREVIOUSLY DISCHARGED MIXTURE TO FORM A VISCOSE SOLUTION HAVING AN ALKALINITY BETWEEN ABOUT 5% AND 8% NAOH BY WEIGHT; THEREAFTER INTRODUCING ANOTHR QUANTITY OF ALKALI CELLULOSE INTO SAID CHURN WHILE SAID CHURN IS STILL WET WITH SCAVENGING SOLUTION; AND REPEATING THE CYCLE. 